The present invention generally relates to methods and apparatus for determining the fluid level of a container, such as an accumulator, and more specifically, to methods and apparatus for determining the fluid level of a container without the need for either electrical power or a direct line of sight to the container.
Accumulators are frequently used on military and commercial aircraft to accommodate the thermal expansion of coolant and hydraulic fluids. During aircraft servicing, maintenance personnel need to ascertain if the accumulator contains the appropriate fluid level. Often, the accumulator is located in an inconvenient space for visual inspection and there is no aircraft electrical power available to operate a level sensor. Fluid volume, or level, is one of the primary service needs of these types of systems.
One of the methods of monitoring the fluid volume has been a dial or gage directly mounted on the accumulator. This type of indicator would allow a direct reading of the accumulator piston's stroke with either a window to see the piston, or possibly a cable and drum system attached to the piston. This type of directly mounted gage is typically used by the technician during refilling of the accumulator. For periodic inspection and monitoring of fluid level, however, the directly mounted gage may be difficult to access by the technician.
Another method of monitoring the fluid volume in an accumulator is to have a remote quantity indicator. This can either be a mechanical or electrical type of indicator. A remote fluid volume indicator could prove to be better for periodic inspection, but may not be the preferred indicator for a service technician.
As can be seen, there is a need for a quantity level indicator for an accumulator that can indicate the fluid level both directly and indirectly.